The human body includes biometric information that may identify an individual, some of which is used as information for identifying and authenticating an individual. For example, it is known that there are fingerprint, eye retina and iris, face, blood vessel, DNA (Deoxyribo Nucleic Acid) or the like, as biometric information available for authentication.
With the recent development of biometric authentication technology, a variety of apparatuses have been provided which recognize such characteristics of living body as a part of the human body, and perform personal authentication. Biometric authentication is performed by comparing the biometric information collected at the time of registration (registered template) with the biometric information obtained at the time of authentication.
In order to improve the precision of the authentication based on biometric information, it is desirable to obtain biometric information with a certain precision each time authentication is performed. However, the user to be authenticated does not always take a proper posture when authentication is being performed. Accordingly, there has been proposed a biometric authentication apparatus which guides biometric information to a proper position in order to obtain biometric information which may be compared with a registered template. For example, a biometric authentication apparatus using a vein of a palm detects displacement of the palm, and guides the palm to a position overlapping with the registered template (see Japanese Laid-open Patent Publication No. 2008-71158, for example).
However, guiding the living body to a proper posture frequently, or each time authentication is performed, may result in an evaluation by the user that the biometric authentication apparatus is not user-friendly. Particularly, around the boundary of whether guidance of the living body to a proper posture is needed or not, the user may have an experience such that, although the user recognizes that the living body is taking a proper posture, the living body is guided to a different proper posture from that of the user's recognition, or the living body is not guided to a proper posture although the user doubts if the living body is taking the proper posture. Such an experience makes it difficult for the user to recognize a truly proper posture. In addition, a biometric authentication apparatus providing such an experience is not convenient for a user, and thus it is desired to reduce the guidance frequency around the boundary of whether guidance of the living body to a proper posture is needed or not.